The present invention relates generally to a zoom lens and an electronic imaging system using the same, and more particularly to a zoom lens, the depth dimension of which is diminished by providing some contrivance to an optical system portion such as a zoom lens, and an electronic imaging system using the same, for instance, a video or digital camera.
In recent years, digital cameras (electronic cameras) have received attention as the coming generation of cameras, an alternative to silver-halide 35 mm-film (135 format) cameras. Currently available digital cameras are broken down into some categories in a wide range from the high-end type for commercial use to the portable low-end type.
In view of the category of the portable low-end type in particular, the primary object of the present invention is to provide the technology for implementing video or digital cameras whose depth dimension is reduced while high image quality is ensured, and which are easy to handle. The gravest bottleneck in diminishing the depth dimension of cameras is the thickness of an optical system, especially a zoom lens system from the surface located nearest to its object side to an image pickup plane.
To make use of a collapsible lens mount that allows the optical system to be taken out of a camera body for phototaking and received therein for carrying now becomes mainstream. Typical examples of an optical system that can effectively be slimmed down while relying on the collapsible lens mount are disclosed in:                JP-A 11-194274        JP-A 11-287953        JP-A 2000-9997These optical systems comprise two lens groups, i.e., in order from their object sides, a lens group having negative refracting power and a lens group having positive refracting power, both of which move upon zooming.        